Binaural recording and reproducing sound



Sept. 30, 1930. L. DE FOREST I 7,

BINAURAL RECORDING AND REPRODUCING S OUND I Original Filed Nov. 27, 1926Lea De Hares).

Patented Sept 30,, 19363 antral era than? m roansr, or new roan, n. r,Assreuon TO DE roans'r rHoNoriLm consona- TEQN, 33 33 NEW YORK, N. Y", A

conrons'rron or DELAWARE BEHAUEAL BEEQEDING- .[iND REPBQDUGING SOUNDfiriginal application flied Ifovember a7, 1926, Serial No. 151,170.Bivided and this application filed August 4, 29558.

This invention relates in general to talking motion pictures.

One of the objects of this invention is the v provision of a new andnovel apparatus for the reproduction of sounds in connection with motionpictures which are a faithful reproduction of the original sounds fromwhich they are made.

Another object of this invention is the pro vision of a new and novelapparatus by means of which several sound records from the same sourcemay be simultaneously recorded onithe same or separate film negatives. I

Another object of this invention is the constructionpf a single positivefrom this negative having thereon the twosound records in superimposedposition and of a different color.

A further object of this invention is the provision of a new and novelarrangement of devices by means ofwhich the sound may be reproduced at aplurality of points from th above described composite film.'

A still further object of this invention isthe provision of soundreproducing, apparatus of this nature in which two photo-electric cellssensitive to light waves of different wave lengthsare exposed to thelight of different gave lengths coming from such a composite A furtherobject of this invention is to provide apparatus which is adapted toselectively disassociate the sound records on such a composite film, soas to make them available for actuating photo-electric cells sensitiveSerial no. 297,507. 7

same reference numerals will be used for parts in the diiierent views toindicate the same or similar parts. a

Figure 1 is a diagrammatic view with the film gate in verticalcross-section of the apparatus for recording sound;

Fig. 2 is a frontelevational view of a film on which the two recordsfrom the same Fig. 4 is a side elevational view of a composite filmhaving the two superimposed sound records thereon.

In my copending application'Serial No. 121,67 9, filed July 10, 1926, Ihave disclosed a system for recording simultaneously two distinct soundrecords from the same source and reproducing each by means of loudspeaking devices located at different points with respect to a motionpicture screen, The

sound records which are simultaneously recorded from the same source ofsound are made from apparatus employing a mlcrophone for each record"located at difierent points with respect to the same source of sound. Inthat system'two sound records are photographically recorded on the samestrip of film, one -for each source, using distinct microphones, twoamplifiers, and two sources of variable light; and in reproducing twosources of light and two photoelectric cells each with its own amplifierand loud speaker. As stated above, these loud speakers are arrangedrelative to'the screen in positions corresponding in a manner to theoriginal location of the two microphones with respect to the soundsource.

The method there described requires two distinct'sound records,preferably arranged, one on either side of the motion picture film.

In the present apparatusl employ a single composite film comprising twoseparate positives, each having thereon a separate sound record madefrom the same source, thereb obtaining the benefits of so-calledbin-aural reproduction Without encroaching upon the space of the filmreserved for the, picture in any greater degree than is at presentrequired for'the single sound record.

It has been known that two sets of photographs can be printed on thesame strip in difi'erent colors, for example in red and blue-one on oneside of the film and one on the other side, or both on the same side ofthe film, one color picture being superimposed upon the other. I utilizethis principle in recording two sound records on the same strip, one ,inred and one in blue.

Referring to the drawings, there is shown in Fig. 1 at I, a film gatehaving two fine slits 2 and 3 therein past which there is adapted to bemoved a motion picture film 4 in close proximity thereto. Mounteddirectly in back of the slits 2 and 3 are the light sources 5 and 6,which are respectively connected by means of the wires 9 and 10 to anysuitable v current amplifying devices 7 and 8, respec- 'tively. As oneform of amplifier suitable for this purpose, I have indicatedby the drawings. a vacuum tube type. The amplifiers 7 and 8 are connected,respectively, by means of cables 13 and 14 to the sound sensitive deviceor microphones 11 and .12. It will be apparent from this drawing anddescription when the microphones 11 and 12 are placed at the properdistance and at different points with respect to the same source thateach light source will receive substantially the same currentsrepresenting the sounds from this source, but they will have somedifferences due to the spacial relation which they bear to the soundsource.

It is import-ant to note that the two slits 2 and 3 are not in verticalalignment with each other as will be apparent upon examination of Fig.2. The two slits have been indicated by the black lines 2 and 3 on eachside of the film 4 so that the sound record will be made along eachmarginal edge of the film. For clarity, it may be stated again thatthese sound records will vary somewhat due to their different positionof their respective microphones, with respect to the sound source. WhileI have shown the sound records applied to the marginal edges of the film4 it will be apparent there would be no substantial deviation from thisinvention by recording them at other points on the film 4,-

or even on separate films.

It will be apparent that this apparatus is essentially adapted forrecording sounds of all the instruments in the orchestra by employingtwo microphones. It is, of course,

I evidentthat a-plurality of microphones could be utilized. and forinstance, twomicro phones could be substituted for the micro- The twosound records on the film 4 are printed, each on separate positives, sothat one positive carries the record made through the slit 2 and theother the record made through the slit 3.

While I do not desire to be limited to the particular point on the filmswhere the records are printed, l have found that it is preferable torecord them at one of'the marginal edges thereof. It is important tonote that these sound records are printed on their positives, so thatwhen one is superimposed over the other, the two sound records may bejuxtapositione'd or juxta-opposed, so that one lies directly above theother and not on opposite sides of the final positive, as was the casewith the original negative. One of these positives is then dyed onecolor and the other is dyed another. For instance, one may be dyed blueand the other red. The two dyed positives are then cemented together insuch a manner that the red sound record lies exactly over the blue soundrecord in the mannerv indicated above. double positive in Fig. 4, inwhichthe two films cemented. together have been indicated at 15 and 16,it being intended that 15 represents the film which lies in back of film16.

Thus, as described, the film 15 would have I have shown such a,

and 16 moves over the surface of the gate, as

shown in close proximity thereto. The light from the two sources 17 and18 pass through the colored filters 24 and 25, respectively.

The colored filter in front of the slit 22 is a red light filter, which,as will be readily understood, transmits light in the Wave lengthsrepresenting the red light, and the filter 25 in front of the slit 23 isa blue filter which transmits or permits only bluelight to pass. The redlight transmitted by the filter 24 impinges upon a photo;electric cellof the thalofide type 26, which is especially sensitive to red orinfra-red light. The blue light which is transmitted by the filter 25falls upon a photo-electric cell of the potassium mirror type 27, whichis sensitive to green, blue or ultra-violet light. As is clearly shown,the photo-electric cell 26 is connected by means of the wire 28 to aVacuum tube amplifier 20, and

the electric cell 27 is likewise connected by means of the wires 29 to asimilar vacuum tube amplifier 31. As I stated in connection with theamplifiers 7 and 8, it will be apparent that the amplifiers 30 and 31may be of any suitable form, and those disclosed by me in a diagrammaticsense are only to be taken as illustrative. The cables 32 and 33 fromthe amplifiers 30 and 31, respectively, are connected to theelectromagnetic sound reproducing units 34 and 35 of the loud speakinghorns 36 and 37 as shown. These horns are disposed with respe ct to themotion picture screen 38 in the manner best suited to produce the effectthat the sound is emanating from two or more sources simulating theoriginal sound sources.

I have indicated in Fig. 1, at 40 on the composite film 15, 16, thesound record which is composed of the two separate sound records, aspreviously described, including red and blue markings. In the reproducmgapparatus the disposition of the slits 22 and 23 are shown on Fig. 4 bythe short heavy black lines, also represented by the references 22 and23.

It may be noticed that in this apparatus, as opposed to the recordingapparatus of, Fig. 1, the two slits 22 and 23 are in vertical alignmentand displaced vertically with respect to each other a distance equal tothe vertical dis-- placement between the two slits 2 and 3 so that thesounds represented by the red and blue records will be simultaneouslyreproduced by the horns 36 and 37. It hardly need be stated here that ifdesired more than two .loud speaking devices may be utilized anddisposed at any suitable points with respect to the screen 38.

By this arrangement each loud speaker will reproduce only the soundwhich is represented by one of the sound records on the composite film.It will also be evident that I have provided apparatus for selectivelydisassocis ating the two different colored superimposed sound recordswhich are on the composite film 15 and 16, so that the twophoto-electric cells sensitive to light of different wave lengths may besimultaneously and individually actuated.

It will be readily apparent to those who are skilled in this art thatthere are many changes in the details of construction and relativearrangement of parts, as well as in the steps of the method and relativearrangement, which will readily occur to them. and I do not, therefore,desire to be particularly limited to the exact disclosure which I havepresented in this specification and drawings, for the purpose ofillustrating the principlesof my invention. I desire only to be limitedto the scope of my invention, as I have defined it in the appendedclaims.

What I seek to secure by United States Letters Patent is:

1. ,Apparatu's for the bin-aural reproducing of sound comprising a filmhaving differently colored sound records thereon superimposed one on theother and longitudinally spaced apart one with respect to the otherplaced between sources of light and light actuated cells sensitive todifferent wave lengths and means separately actuated b the currentsgenerated in each of said cells or producin sound.

2. In sound reproducing apparatus, the combination with twophoto-electric cells having different color response, characteristics,two light sources, a film having thereon two superimposed longitudinallyspaced apartdifferently colored sound records, a 'film gate having twolongitudinally spaced apart slits thereon between said sources andcells, a light filter between each slit and cell for transmitting lightof a different wave length, of a separate sound reproducing deviceconnected to each cell.

3. The combination of a sound photographie film having separate anddifferent sound records superimposed one on the other, butlongitudinally displaced one'with respect to the other, and separatelongitudinally separated means for reproducing the sounds from each ofsaid records without interference one from the other.

4'. In a bin-aural sound reproducing apparatus the combinationcomprising a film having two superimposed, distinct sound records ofdifierent colors linearly displaced, light sources on one side of thefilm, so the light therefrom shines through said records, slit formingmember between the light sources and the film, light sensitive cells,color filters between the film and cells and a separate soundreproducing device connected to each cell.

5. In sound reproducing apparatus, the

